The Publication No. S63-129775 of the Japanese Unexamined Patent Application discloses an image forming apparatus designed to be operated manually. The image forming apparatus has a manually movable housing having a thermal print head protruding downward from its bottom. In the housing are provided an ink film holder for holding a roll of thermosensitive ink film and a film winder for winding a used part of the ink film. When the housing is manually moved on a surface of a print object, the ink film is fed from the ink film holder past a heating part of the print head, while the heating elements in the heating part are driven according to a dot pattern of an image data with respect to the amount of movement of the housing.
The Publication No. H8-1096 of the Japanese Examined Utility Model Application discloses another image forming apparatus using a manually movable housing having a wire dot type of print head. In the housing are provided a film-feeding roller for holding an ink donor film and a film winder for winding a used part of the ink donor film. When the housing is manually moved on a surface of a print object, the ink donor film is fed from the film-feeding roller past the print head, and the wires of the print head are driven to strike the ink donor film according to a dot pattern of image data with respect to the amount of movement of the housing.
The above-described image forming apparatuses have the following drawbacks. First, a supplemental device is necessary for the input and storage of image data. Second, when a user intends to form images on a number of sheets of print media, for example, the user has to carry out time-consuming work including steps of securing a sheet of print medium by hand or by other means on the desk or the like, and moving the housing manually on the print medium. In such a case, it is recommended to use another type of image forming apparatus wherein a print head is mechanically driven back and forth in the direction vertical to a feed path into which a feeding mechanism feeds the print medium, one sheet after another, past the print head from a stack of print media. This type of image forming apparatus, however, cannot be used when the user intends to form an image on a medium or object that is too thick and/or stiff to be fed by the feeding mechanism.